275/45 R21
What size is 275/45 R21?
275/45 R21 has an overall diameter of about 30.74 in, a section width of 10.83 in and a sidewall height of 4.87 in. It turns roughly 656 times per mile. Below are the exact figures plus in-tolerance plus/minus sizes you can switch to safely.
- Overall diameter: 30.74 in.
- Section width: 10.83 in.
- Sidewall height: 4.87 in.
- Revolutions: 408 /km · 656 /mi.
- In-tolerance sizes: 265/70 R16 (-0.4%).
Fitment verdict
265/70 R16 stays within the configured tolerance for 275/45 R21: -0.4% diameter and -0.4% speedometer effect.
| Metric | This size: 275/45 R21 | Alternative: 265/70 R16 | Difference | Verdict |
|---|---|---|---|---|
| Overall diameter | 30.74 in | 30.61 in | -0.4% | Within tolerance |
| Section width | 10.83 in | 10.43 in | -0.39 in | Computed difference |
| Sidewall height | 4.87 in | 7.30 in | +2.43 in | Computed difference |
| Circumference | 96.59 in | 96.15 in | -0.4% | Within tolerance |
| Speedo | 0.0% | -0.4% | -0.4% | Within tolerance |
Seasonal check
Planning a long summer drive?
Use the budget and running-cost tools before a trip, especially if the current tyres are worn or the replacement size changes diameter.
Specification
| Overall diameter | 30.74 in |
|---|---|
| Section width | 10.83 in |
| Sidewall height | 4.87 in |
| Circumference | 96.59 in |
| Revolutions | 408 /km · 656 /mi |
In-tolerance sizes
Alternative sizes that stay within the safe diameter tolerance:
| Size | Diameter | Speedo | Verdict |
|---|---|---|---|
| 265/70 R16 | -0.4% | -0.4% | ✓ OK |
| 275/55 R19 | +0.5% | +0.5% | ✓ OK |
| 265/65 R17 | -0.6% | -0.6% | ✓ OK |
| 245/65 R18 | -0.7% | -0.7% | ✓ OK |
| 265/60 R18 | -0.7% | -0.7% | ✓ OK |
| 285/40 R22 | +0.8% | +0.8% | ✓ OK |
| 245/70 R17 | -0.8% | -0.8% | ✓ OK |
| 31x10.50 R15 | +0.8% | +0.8% | ✓ OK |
| 31x10.50 R16 | +0.8% | +0.8% | ✓ OK |
| 265/50 R20 | -1.0% | -1.0% | ✓ OK |
| 265/45 R21 | -1.2% | -1.2% | ✓ OK |
| 265/40 R22 | -1.3% | -1.3% | ✓ OK |
Compare sizes
- Within tolerance · Diameter -0.4%.
- Speedo @ 60: 60 mph → 59.7 mph.
- Sidewall +2.43 in · Width -0.39 in.
How this result is calculated
Computed from nominal tire-size geometry: diameter, circumference and speedometer error. It does not check wheel-arch, suspension or brake clearance.
Methodology- Diameter
- 30.74 in 30.61 in-0.14 in
- Sidewall
- 4.87 in 7.30 in+2.43 in
- Width
- 10.83 in 10.43 in-0.39 in
- Circumference
- 96.59 in 96.15 in-0.4%
- Revs / mile
- 656 659
- Speedo @ 60
- 60 mph 59.7 mph-0.4%
- Current —
275/45 R21 - New —
265/70 R16 - Grounded to the road: the axle rises -0.07 in.
Result report
275/45 R21 265/70 R16 · Within tolerance
Use this size when shopping: 265/70 R16
Geometric estimate. Always verify physical clearance (arches, suspension, brakes) before fitting.
Safe alternative sizes
| Size | Diameter | Speedo @ 100 | Use this |
|---|---|---|---|
−1″ 195/70R20 | +0.0% | +0.0% | |
OE 275/45R21 | +0.0% | +0.0% | |
+1″ 185/60R22 | -0.0% | -0.0% | |
+2″ 245/40R23 | -0.1% | -0.1% |
More tools
- How to read a tire size
- Plus sizing guide
- Speedometer error guide
- 275mm Section width guide
- /45 Aspect ratio guide
- Rim diameter 21"
- Load index chart
- Speed rating chart
- Rim width and tyre fitment guide
- Wheel offset guide
- Wheel spacers guide
- Tyre pressure for heavy loads and towing
What changed
- Reviewed deterministic geometry, load/speed references, sitemap inclusion and localized page shell.